Super cooler for a heat producing device

ABSTRACT

A super cooler device including a thermo electric cooler on a digital micro mirror device.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. application Ser. No.10/128,774, filed Apr. 22, 2000, which is a divisional of U.S.application Ser. No. 09/780,025, filed Feb. 9, 2001, which claimspriority to U.S. application serial No. 60/181,530 filed Feb. 10, 2000.

SUMMARY

[0002] The present application relates to cooling of a heat producingdevice, using a thermoelectric cooler arranged as a super cooler. Morespecifically, the present application teaches cooling of a device, suchas a digital mirror device, which requires a specified temperaturegradient across the device, using a supercooled element.

BACKGROUND

[0003] Electronic devices often have specified cooling requirements. Onedevice that has specific cooling requirements is a digital micromirrordevice (“DMD”) available from Texas Instruments (“TI”). The manufacturerof this device has specified a maximum overall temperature for thedevice and also a specified maximum temperature gradient between thefront and rear faces of the device during operation.

[0004] For example, the temperature of the specific DMD used in thisapplication needs to be kept below 55° C., however, in this applicationit is desirable to keep the device at or-below ambient. This may allowoperation in an ambient environment up to 55° C., such as may beencountered in a stage theater or studio environment. The temperaturedifferential between the front and rear of the DMD cannot exceed 15°.Besides the heat from the operation of the DMD itself, large amounts ofheat from a high intensity light source must be dissipated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] These and other aspects will now be described in detail withreference to the accompanying, wherein:

[0006]FIG. 1 shows an exploded diagram of the parts making up thesupercooler assembly;

[0007]FIG. 2 shows the rear of the DMD and parts which are assembled tothe DMD;

[0008]FIG. 3 shows a circuit for driving a thermoelectric cooler; and

[0009]FIG. 4 shows a flowchart of operation.

DETAILED DESCRIPTION

[0010] According to the present system, a “supercooler” device, is usedto monitor and control the temperature of a device which can controllight on a pixel-by-pixel basis, e.g. a digital mirror device (DMD).

[0011] The mechanical structure of the supercooling assembly is shown inFIG. 1. The pixel element is a DMD 99, which forms part of a DMDassembly 100. As shown, a thermal connection 105 to the DMD 99 isprovided.

[0012] A cold plate 120 is assembled to a mounting bracket 110 in amanner which allows minimal thermal transfer between the two components.The DMD is attached directly to the cold plate 120, hereby allowingmaximum thermal transfer between the DMD and cold plate 120, but minimalthermal transfer to the mounting bracket 110. The rear surface of thecold plate 120 is directly connected to one side of the thermoelectricdevice 130, and the other side of the thermoelectric device is connectedto a heat sink/fan assembly 140.

[0013] Insulating foam gaskets are fitted around the DMD rear stud, thecold plate, and the thermoelectric device in order to isolate them fromthe outside ambient air. This improves the efficiency of the coolingsystem by eliminating the effects of condensation and properlycontrolling the flow of heat from the DMD to the cold plate, through thethermoelectric device, and into the heat sink/fan assembly.

[0014] The thermoelectric cooler element 130 operates as conventional toproduce one cold side 131 and one hot side 132. The hot side is coupledto the heat sink/fan assembly 140 to dissipate the heat. In a preferredmode, the heat sink/fan assembly is columnar is shape, with asubstantially square cross section. This facilitates using a squareshaped fan housing 142. The square shaped fan unit allows the maximumuse of the space for a fan, whose blades usually follow a round shape.Any type of cooling fan, however can be used.

[0015] The DMD assembly 100 has an extending rear stud 105 which iscovered with thermal grease. This stud extends though a hole 112 in thebracket assembly 110.

[0016] The plate 120 is actively cooled, and hence becomes a “coldplate”. The active cooling keeps the metal plate at a cooledtemperature, and the thermal characteristics of the plate material allowthe heat flowing into the plate from the DMD to be evenly distributedthroughout the entire plate. The plate is preferably about ¼″ to ⅜″ inthickness, and of comparable outer size to the thermal contact area ofthe thermoelectric cooler element 130. This allows the localized andconcentrated heat at the rear stud of the DMD to be evenly dissipatedthrough the cold plate and then efficiently transferred through the fullsurface area of the thermoelectric cooler element. As shown, theassembly employs thermal insulation techniques such as fiber/plasticsleeves and washers in the mounting of components, in order to preventheat transfer via mounting screws etc. Since this heat transfer could beuncontrolled, it could otherwise reduce the cooling efficiency.

[0017] The front of the DMD is shown in FIG. 2. Temperature sensor 200is mounted to have a fast response to temperature changes. A secondtemperature sensor 122 is mounted to the cold plate 120 and effectivelymeasures the temperature of the rear of the DMD 99. This secondtemperature sensor 122 therefore monitors the back temperature.

[0018] The hot side 132 of the thermoelectric cooler is coupled to aheat sink assembly 130. The heat sink assembly 140 includes a heat sinkelement 140. As shown, the device has fins and a top-located cooling fan142.

[0019] A block diagram of the control system is shown in FIG. 3.Controller 300 operates in a closed loop mode to maintain a desiredtemperature differential across the sensors 122, 200.

[0020] One important feature of the present application is that thethermoelectric cooler is controlled to maintain the temperature of theDMD at the desired limits. These limits are set at a target of 16° C. onthe front, and a differential no greater than 15° between front andrear. The thermoelectric cooler is controlled using very low frequencyor filtered pulse width modulation. In a first embodiment, thecontrolling micro controller 300 produces an output 302, e.g., digitalor analog. This drives a pulse width modulator 304. The output of thepulse width modulator is a square wave 306 or a signal close to a squarewave, with sufficient amplitude and power to produce the desired levelof cooling down the thermoelectric cooler. The square wave is coupled toan LC filter 308 which has a time constant effective to smooth the 20KHz switching frequency. The output to the thermoelectric cooler istherefore a DC signal. This drives the thermoelectric cooler 130 andcauses it to produce a cooling output. In a second embodiment, the LCfilter is removed and the TEC is driven directly by the square wave 306at a lower frequency, e.g. 1 Hz.

[0021] The microcontroller operates according to the flowchart of FIG.4. Step 400 determines if the temperature of the first temperaturesensor T1 is greater than 16°. If so, the output to the TEC remains“on”, resulting in further cooling. When the temperature falls below16°, the drive to the TEC is switched off. The sample period isapproximately ½ second between samples.

[0022] At 410, the system checks temperature of the first sensor (T1)and of the second sensor (T2) to determine if the differential isgreater than 15°. If so, the output is switched “on”. Step 420 indicatesa limit alarm, which represents the time of increase if the rate ofchange continues. If the rate of change continues to increase, asdetected at step 420, a fault is declared at step 425. This fault cancause, for example, the entire unit to be shut off, to reduce the powerand prevent permanent damage.

[0023] Other embodiments are contemplated.

What is claimed:
 1. A system, comprising: a mounting plate, havingmounting holes at locations and having sizes which are adapted formounting a digital mirror device, said mounting plate also having anopening sized to receive a heat stud of the digital mirror deviceattached therethrough; and a cooled plate, thermally coupled to saidheat stud, and actively cooled to thereby cool the heat stud of thedigital mirror device while minimizing an amount of heat transfer to themounting plate.
 2. A system as in claim 1, wherein said cooled plateincludes a fan and heatsink assembly, coupled to a surface of saidcooled plate, operating to remove heat from said cooled plate.
 3. Asystem as in claim 1, wherein said cooled plate includes an activecooling unit, which produces a cooling amount based on appliedelectrical energy.
 4. A system as in claim 3, wherein said activecooling unit includes a thermoelectric unit.
 5. A system as in claim 1,further comprising a digital mirror device, connected to said mountingplate, and having said stud extending through said opening.
 6. A systemas in claim 5, further comprising thermal insulation elements, whichthermally insulate portions of said digital mirror device from ambientair.
 7. A system as in claim 4, further comprising thermal insulationbetween said digital mirror device and said mounting plate.
 8. A system,comprising: a digital mirror device; a mounting assembly for saiddigital mirror device; a cooling assembly for only a rear side of saiddigital mirror device; and a control system, which controls said coolingassembly, to control at least one aspect of cooling of said coolingassembly.
 9. A system as in claim 8, wherein said cooling assemblyincludes a metal plate which is actively cooled.
 11. A system as inclaim 9, wherein said control system controls a temperature of saidcooled plate.
 11. A system as in claim 10, wherein said cooling assemblyincludes an electrically controllable cooler.
 12. A system as in claim11, wherein said electrically controllable cooler includes athermoelectric cooler.
 13. A system, comprising: a digital mirrordevice, having a first mounting surface; and a second optically activesurface; and a cooling part for said digital mirror device including atleast a heatsink and a fan, said fan being mounted to blow in adirection that is away from both said first and second surfaces of saiddigital mirror device.
 14. A system as in claim 13, wherein said coolingpart is thermally coupled to said digital mirror device.
 15. A system asin claim 13, the further comprising a metal plate, thermally coupledbetween said cooling part and said digital mirror device, said thermalplate being cooled by said cooling part.
 16. A system as in claim 13,further comprising a control system, which controls an amount of coolingof said cooling part.
 17. A system as in claim 16, wherein said coolingpart includes an active cooler, which produces an amount of cooling thatis proportional to an amount of applied electricity.
 18. A system as inclaim 17, where in said control system controls an amount of cooling bysaid active cooler.
 19. A system as in claim 17, further comprising ametal plate, thermally coupled between said cooling part and saiddigital mirror device, said thermal plate being cooled by said coolingpart, and wherein said control system controls an amount of cooling bysaid cooling part to thereby effectively control a temperature of themetal plate.
 20. A system, comprising: a digital mirror device, having afront optically active surface and a rear surface; a metal plate,thermally coupled to said rear surface, and thermally in contact with aheated part of said rear surface; and a temperature controlling part,actively maintaining a temperature of said metal plate at a specifiedamount.
 21. A system as in claim 20, further comprising an activecooler, included in said temperature controlling part, which produces anamount of cooling that is proportional to an amount of appliedelectricity.
 22. A system as in claim 20, wherein said active cooleralso includes a heatsink and fan, said fan mounted to blow air away fromsaid digital mirror device.
 23. A method, comprising: operating adigital mirror device; and actively cooling said digital mirror deviceusing an active cooler which produces cooling effect in proportion to anamount of applied electricity.
 24. A method as in claim 23, wherein saidactive cooler is a thermoelectric cooler.
 25. A method as in claim 23,wherein said active cooling comprises providing a metal plate in thermalcontact with said digital mirror device, and actively cooling saidthermal plate to maintain said thermal plate in a desired thermal state.26. A method as in claim 23, wherein said active cooler includes anelectrical cooling device, and a heatsink which dissipates heat fromsaid electrical cooling device.
 27. A method as in claim 23, furthercomprising monitoring a temperature of said digital mirror device.
 28. Amethod, comprising: operating a digital mirror device which has a frontsurface and a rear surface; cooling only one surface of said digitalmirror device; and monitoring temperatures of both surfaces of saiddigital mirror device.
 29. A method as in claim 28, further comprisingcontrolling said cooling to maintain a desired temperature differentialbetween said surfaces of said digital mirror device.
 30. A method as inclaim 28, wherein said cooling comprises active cooling using anelectrically controllable cooler that produces an amount of coolingproportional to an amount of electricity applied thereto.
 31. A methodas in claim 30, wherein said monitoring temperatures comprisesmonitoring temperatures of said surfaces, and controlling said amount ofelectricity based on said temperatures.